Telephone-exchange system.



. PATBNTED MAR. 27, 1906.

; W. M. DAVIS.

TELEPHONE lXgANGrE` SYSTEM.

APPLICATIONv FILED AUG.5.1901.

UNTTED STATES PATENT @Finca-.

vWILLIAM DAVIS, CHICAGO, ILLINOIS, ASSIGNOR, BY MESN ASSIGNMENTS, TOSTROMBERGr-OARLSON TELEPHONE MANUFAO= TURING COMPANY, OF ROCHESTER, NEWYORK, A CORPORATION OF NEW YORK.

, vTELEPHONE-'Excl-IA'NGE SYSTEM. l

Specification of Letters Patent.

Patented March 27, 1906.

Application led August 5,1901. Serial No. 70,924.

To au 'wh/om it ,may concern: Be it known that I, WILLIAM M. DAVIS, a`Citizenof the United States, residing at Ohicago, in the county of Cookand State of Illinois, have invented a certain new and usefulvImprovement in Telephone-Exchange Sys-Y call to interrupt the circuitincluding the linerelay, whereby the line-indicator is renderedinactive.V Heretofore for the purpose of con-v trolling the operationofthe cut-,off relays.

the cordcircuit. has been equipped with a third cord=strand terminatinginl a third contact part carried by the plug, which third contact partconstituted one terminal of the cir-v cuit, including the cut-off relay,the other ter- IrlI'lal usually residing in a metallic' thimble locatedbefore the jack. I t is an object of my invention to equipa relayswitchboard in a manner to dispense with this third conductor,

feature of the invention may be employed in connection with all types ofmultiple boards employing relays ,for controlling the line-indicators.

A second feature of the invention relates particularly to multipleswitchboards, and consistsin means whereby the thimbles of the sprinjacks of each subscribersline arevv connecte in a test-circuitimmediately upon the removaliof the receiver at the calling subscribersstation, are preventedfrom e'ec'ting connection with a, callingsubscriber with whom another subscriber may desire connection, eventhough the callingv subscriber has not been answered by hs'operator. Asis well known, test-thimbles are usually not charged with test-batte13TY orotherwise operatively associated with the Bythis means operatorstest-circuit until the calling subscriber has been answered. vAs theoperators may defer plugging into the jacks of calling subscribers untiltheir connections have been completed, an interval may arise in whichthere are no `means of determiningthe condition of thecalling-subscribers line as this line may'then be tested Not busy, sothat the callingsubscriber may then undesirably be ,connected withanother calling subscriber wishing oo nnection withhim.

I practice the first feature of my invention by providing switchingapparatus that serves to include the heliX'ofthe cut-0E relay in bridgeof the telephone-line, in which bridge is preferably included a sourceof current. A relay is preferably provided whosey armav'ture in itsnormally unattracted position serves momentarily toy close circuitthrough vthe cut-off relay, not by including this relay in bridge of thetelephone-line, but momentarily establishing a local circuit therefor asthe plug enters the jack, the armature of the re. lay being includedinthis local circuit. When the plug has been fully inserted within the ljack, the latter relay is operated to open the local circuit; vbut thecut-off relay, having been previously ener ized to include the same inbridge of the telep one-line, remains in this relation to the line untilthe plug is withdrawn.

In practicing the second feature of In invention, which is designed formultipleswitchboard telephone-exchange systems, I employ a relay, whichmay be theaforesaid line-relay, and provide a switch.` to be .controlledthereby, which is operated'when a subscriber operates the said relayyupon removing his receiver from its hook' toconnect testing-batterylwith' the` test contacts or thimbles of the spring-jacks of the said'line upon the various sections of the multiple board. The operator thusdoes not control" the charging of the test-thimbles, thiscontrol beingeffected by thejcalling subscriber'.V

I will explain my invention more fullyY by reference to the accompanyingdrawing, in which the figure is a diagrammatic viewillustrating atelephoneexchange system embodying the features of my invention.

At the substations and 120 are illustrated IOO well-known types oftelephonie apparatus.

At each station there is provided a'signal-re-- ceiver 1, atelephone-transmitter 2, a primary winding 3, and a switch-hook 4 forincluding the bell 1 in circuit when the receiver 5 is in .place uponthe hook and for excluding this bell from circuit and including insteadthereof the transmitter 2 with the primary winding 3 when the receiveris removed from its hook.

There is included in a local circuit with the receiver 5'the secondary 6of a transformer. Other types of telephone-station apparatus, however,may be employed without departing from the spirit of my invention.yTelephone-lines extend by their limbs 7 and 8 to the armatures 9 and 10of a cut-off relay 11. The limb 7 then extends when the armature 9 is,in engagement with its normal contact through the winding of theline-relay 12 to one terminal of the common battery 13, in this instancethe positive terminal, the limbs 7 thus when idle having commonconnection with this terminal of the battery. The limb 8 byreason of theengagement of the armature with its normal contact is normally connectedwith the remaining terminal ofthe common battery. Thus the commonbattery is normallyin bridge of the telephonelines but the condensers 15at the substations prevent the flow of this battery by way of thetelephone-lines when the telephone-receivers are upon theirswitch-hooks.

When a subscriber initiates a call by removing his receiver from itstelephone switch-hook, the common battery 13 is closed through thewinding of the relay 12, which thereupon attracts its armature, therebyuniting the contacts 16 17 to actuate the corresponding line-indicator18, that is thus included in a local circuit with the common battery,and also closes the contacts 19 and 20 together, whereby one terminal ofthe common battery, in this instance the positive terminal, is connectedwith the test-thimbles 21 of the spring-jacks 22, distributed over thevarious sections of the multiple switchboard.

Itwill be observed that the tes't conditions are automatically suppliedby the calling subscriber when he removes his telephone from theswitch-hook. The test-controlling mechanism operated by the subscriberis thrown out of service when the operator answers his call 5 but thetest conditions are immediately restored through the agency of thesleeve of the answering-plug engaging the test-thimble of the jack andincluding the common battery. The test of course is manifested upon thedepression of the operators listening-key if the line tested elsewhereis busy.

Thus is one object of my invention accomplished-namely, the immediatefulfilment of busy-test conditions for the calling-subscribers line toprevent interference thereof after a call is initiated.

The short line-springs of the various springjacks are adapted forconnection with the limb 8, while the long line-springs are adapted forconnection with the limb 7, these springs being also connected with thetestthimbles. Cord-circuits are employed, one of which is illustrated,comprising in this instance answering and connecting plugs 23 24, thetips whereof are united by a tip-strand, while the sleeves are united bya sleevestrand that includes in circuit therewith the operating helicesof supervisory relays 25 26, a bridge-conductor 27 being includedbetween these helices and including an inductive resistance 28, wherebythe control of these supervisory relays may be independently effected bythe corresponding subscribers apparatus. Each supervisory-relay core isprovided with a supplemental winding 29, these supplemental windingsbeing included in a closed local circuit. These supervisory relayscontrol the supervisory signals 30 31 by means of their armatures 32 33.

As a result of the manipulation of the apparatus to be hereinafter setforth contacts 34 35 are closed to complete a cord-circuit, the armature33 effecting this engagement of the contacts and disrupting thetest-circuit, including the testing-conductor 36, which forms thesubject-matter of my Patent N o. 697,991, issued April 22, 1902.

It will be seen that when a subscribers line is busy a connection iseii'ected between the positive terminal of the battery 18 and thethimbles 21 of the spring-jacks 22, which connection is completedthrough the winding of the relay 12, the armature 20, and thecontact-anvil 19. This condition lasts during the interval of time thatelapses when the subscriber takes his receiver oid the switchhook anduntil connection is eiiected by means of a plug. When connection iseffected, the thimble 21 is still connected to thc positivebattery-terminal, but now receives its current directly from the sleeveof the plug 24, which is directly connected to the positive terminal ofthe battery 13 through the primary winding of the relay 26 and theinductive resistance 28. It will thus be apparent that the thimble 21has at all times positive connection with the source of current when theline is in use. The calling side of the cord-circuit terminating in theplug 24 is used in making a test to ascertain whether a subscribers lineis busy. As this )lug 24 has not been inserted in the spring-jac {of thecalled subscriber, the repeating coil-relay 26 is not energized and theswitch is in its unattracted condition, not engaging its alternatecontact anvil 34. The operator in making the test applies the tip of theplug 24 to the thimble 21, and if the subscribers linel is busy it willbe apparent to the operator, as a circuit is completed through thevarious connections and instrumentalities as follows: from the positivepole of the battery 13, in

IOO

siente tery 13 and the operators head-receiver, may be effected when thetip of the plug 24 comes in contact with the thimble 21,-if the line isbusy. If no cliclris apparent-that is,

if no circuit is Jformed around the battery 13- when the said plugtouches the thimble 21, the line is not busy, as the thimble 21 is thennormally disconnected from the battery. The switch 35 serves to closethe normally disrupted tip-stand of the cord-circuit when the calledsubscriber removes his receiver, the purpose of keeping the tip-strandopen until the parties are ready for conversation being solely to avoidoccasioning a disagreeable click in the receiver of the calling subvscriber while making a test. It will be apparent that il? thetip-strandis not kept open while a test is being made a portion of thecurrent will be diverted through the lsubscribers line `to the negativeterminal of a battery instead of -being constrained, as in the presentcase, to flow altogether through the head-telephone of the operator. .Acondenser 38 is employed, so` that the testcurrent, which may be madelsmall, if desired, will not flow through the secondary ofthe operatorsinduction-coil, but will flow through the head-receiver. The cut-offrelay 11 is in this instance connectedwith the short line-springs `atone terminal and with one pole of the common battery at the otherterminal.. The remaining pole of the common battery is connected withthe tip-strand of the cord-circuit by wayof the clearing-out orsupervisory indicator l30 or 31 corresponding to the particular line,these connections beingv effected by the armatures 32 and 33 when theyare unattracted, so that when a plug is inserted within a jack a localcircuit is momentarily closed, which may be traced (taking the line ofsubscriber 120, for instance) from the short line-spring of the engagedjack, through the winding of the cut-0H relay, the common battery, thearmature 33, its normal contact, the supervisory indicator. 31, tothe'tip-strand and the tip of the plug engaging the short line-spring.Immediately the corresponding relay 26 is energized, disconnectingthelamp 31 from the tip-strand, the winding of the cut-off relay beingthen included in bridge of the telephone-lines, which parallel relationof the cut-oil magnet is maintained until connection between thesubscribers is broken.

The parallel connection of the cut-oli relay 11 may be traced from thetip side of the cord-circuit which is connected with one terminal of thehelix of said cut-0H magnet by the 'engagement of the tip of theinserted plug with the short line-spring, the other terminal ci themagnet 11 being connected with v the sleeve side oi the cord-circuitthrough the battery 13 and the inductive resistance 28. This will bereadily apparent Jfrom the drawing, as the :only connection between thetelephone-lines and the negative terminal of the battery when said linesare united for conversation is completed through the winding of therelay 11, each of the short line-springs of the two talking subscribersbeing furnished with negative current from the'b'attery,while saidline-springs are at the same time metallically connected through thetipstrand oi the cord-circuit, which practically short-circuits the twosprings and places the two relays 11 in parallel between the negativeterminal oi the battery and the said tipstand, thebattery being includedin a bridge oi said cord-circuit. Thus by means of very much simpliiiedapparatus I am enabled to effect a control of the cut-off relay, Jforwhich hitherto it was customary to employ `a third cord-strand and aspecial circuit.

While I have herein shown and particularly described the preferredembodiment of my invention, it is obvious that changes may be madewithout departing from the spirit thereof, and I do not, therefore, wishto be limited to the precise disclosure herein set Jforth; but,

Having thus described my invention, I

claim as new and desire to secure by Letters Patenti 1. Ina'telephone-exchange system, the combination with a telephone-lineextending from a subscribers substation to a central exchange, aplurality of spring-jacks of a multiple switchboard normallydisconnected 'from the line-limbs, a single common source of current atthe central exchange, a line-relay normally connected with theline-limbs through said source of current, a cut-oli relay having alsingle winding, one terminal of said cut-off relay being connected withone terminal of said source and normally with one line-limb, the otherterminal of the cut-oil relay being connected with spring-jack contacts,a cord-circuit for connecting telephonelines together,l actuation ofsubstation apparatus causing energization of said line-relayindependently of the cut-off-relay winding, and means upon connection`oi said cord-circuit'with one oisaid multiple sections for closing alocal circuit containing said cut-offrelay winding and said source ofcurrent whereby said cut-off relay is energized to disconnect. saidline-relay Jfrom circuit, and lto connect the spring-jack contacts withthe line-limbs', said local circuit including one of f the cord-circuitconductors and one limb oit' the telephone-circuit. y l

2. In a telephone-exchangev system, the combination with atelephone-line extending les - from a substation to a central exchange,of a plurality of multiple spring-jacks at the central exchange normallydisconnected from the line-limbs, a single source of current at thecentral exchange for supplying both talking andsignaling currents, aline-relay, a cutofi' relay controlling said line-relay, one terminal ofsaid line-relay being permanently connected with one pole of saidsource, and the other terminal of the line-relay being normallyconnected with one line-limb independently of the cut-oli-relay winding,actu ation of substation apparatus causing a circuit to be completedthrough said line-relay4 and source,.one terminal of said cut-oil-relaywinding being permanently connected with one pole of said source, theother terminal of said Winding being normally connected with a contactof each ofthe multiple spring-jacks, and two strand cord-circuits forconnecting telephone-lines together, one of said strands being normallyconnected with one pole of said source, connection of said cord-circuitwith the spring-jack causing a local circuit to be closed through saidcut-oiI-relay winding, said'source of current, said cord-strand and saidspring-jack whereby said line-relay is rendered inert, a relay forcontrolling said local circuit, the second cord-strand being alsoconnected with the same pole of said source through the winding of saidrelay controlling said local circuit, connection of said cord-circuitwith a spring-jack causing closure of a circuit including said winding,said source of current, said second cord-strand, said spring-jack, saidcut-off-relay winding and the telephone line-limbs and substationapparatus.

3. In a telephone-'exchange system, the combination with atelephone-line extending from a subscribers station to a centralexchange, of a plurality of multiple spring-j acks at the centralexchange, a single source of current at the central exchangeforsupplying talking and signaling currents, a line-relay, a line-indicatorgoverned by actuation of substation apparatus causing actuation of saidline-relay, a cut-off `relay having a single winding for excluding thelinerelay from circuit, cord connecting apparatus for connectingsubscribers for conversation, a local circuit closed by the answeringsaid line-relay,

plug or switch of the cord-circuit upon connection of the cord-circuitwith a springjack, said local circuit including the cut-oil'- Vrelaywinding, said source of current, a telcphonic portion of thecord-circuit and a con ductor portion constituting a continuation of thetelephone-line, a switch included in said local circuit, and a relay inthe cord-circuit for operating said switch, actuation of substationapparatus causing closure of the eircuit through said relay whereby saidswitch is connected to open the local circuit, the circuit through saidrelay including the windin g of said cut-ofi` relay whereby saidline-relay is maintained inoperative. i

4. In a telephone-exchange system, the combination wi th atelephone-line extending from a substation to a central exchange,multiple spring-jacks at the central exchange normally disconnected fromthe line-limbs, a common source of current at the exchange for supplyingtalking and signaling currents, a line-relay, a line-indicator governedthereby, said line-relay being adapted for operation Athrough the agencyof the apparatus at the substation, a cut-oiil relay having a singlewinding for excluding the line-relay from circuit, cord connectingapparatus for uniting subscribers for conversation, connection oi thecord connecting apparatus with a springjack causing closure of a localcircuit, said local circuit serially including the entire cut-oilrelaywinding, a telephonie portion of the cord-circuit, and a conductorportion constituting a continuation of the telephone-lin e,

a switch included in said local circuit, and a relay in the cord-circuitfor operating said switch, actuation of substation apparatus causing theclosure of the circuit through said relay whereby said switch isactuated to open the local circuit, said second circuit seriallyincluding said source of' current, said cut-off-relay winding, acord-circuit conductor and said line-limbs and substation apparatus.

In witness whereof I hereunto subscribe my name this 13th day of July,A. D. 1901.

WILLIAM M. DAVIS.

Witnesses:

GEORG-E L. CRAGG, HERBERT F. OBERGFELL.

